No abstract

Copper(I) cyanide is an important reagent in organic, organometallic, and supramolecular chemistry because of both the copper center and the versatile cyanide ligand. Solid-phase CuCN and many of its derivatives show oligomeric or polymeric structures, a trait shared by other metal cyanides. Often, it is difficult to specify the orientation of the cyano ligand in an X-ray structure. Here the first preparation and precise structure of a monomeric transition metal cyanide is reported. Gas-phase reaction between copper vapor and cyanogen (NCCN) clearly gives CuCN (not CuNC). The precise structure of CuCN so produced is determined by millimeter/submillimeter-wave spectroscopy. Because of the highly efficient synthesis and the presence of significant amounts of two copper isotopes, such strong signals were seen that natural-abundance materials allowed observation of transitions for the four isotopomers (63)Cu(12)C(14)N, (65)Cu(12)C(14)N, (63)Cu(13)C(14)N, and (63)Cu(12)C(15)N and the determination of r(o), r(s), and r(m)((2)) structures. All data unequivocally show a linear geometry and that the carbon of cyanide is bound to copper with a Cu-C distance of 1.82962(4) A in the r(m)((2)) structure, which is likely to be closest to the equilibrium geometry.

Observations of comet Hale-Bopp (C/1995 O1) have been carried out near perihelion (1997 March) at millimeter wavelengths using the NRAO 12 m telescope. The J=1-->0, 2-->1, and 3-->2 lines of HCN at 88, 177, and 265 GHz were measured in the comet as well as the J=3-->2 lines of H13CN, HC15N, and HNC. The N=2-->1 transition of CN near 226 GHz was also detected, and an upper limit was obtained for the J=2-->1 line of HCNH+. From the measurements, column densities and production rates have been estimated. A column density ratio of [HCN]/[HNC] = 7+/-1 was observed near perihelion, while it was found that [HCN]/[HCNH+] greater, similar 1. The production rates at perihelion for HCN and CN were estimated to be Q(HCN) approximately 1x1028 s-1 and Q(CN) approximately 2.6x1027 s-1, respectively, resulting in a ratio of [HCN]/[CN] approximately 3. Consequently, HCN is sufficiently abundant to be the parent molecule of CN in Hale-Bopp, and HCNH+ could be a source of HNC. Finally, carbon and nitrogen isotope ratios of 12C/13C = 109+/-22 and 14N/15N = 330+/-98 were obtained from HCN measurements, in agreement with previous values obtained from J=4-->3 data. Such ratios suggest that comet Hale-Bopp formed coevally with the solar system.

The pure rotational spectrum of the ZnCN radical in its X 2Σ+ ground electronic state has been recorded using millimeter/sub-mm direct absorption techniques in the range 339–543 GHz. This work is the first spectroscopic observation of this molecule, which was created by the reaction of zinc vapor and cyanogen gas in a dc discharge. Twenty-one rotational transitions were recorded for the main zinc isotopomer, ZnCN64, in its ground vibrational state, as well as 8–16 transitions for the Zn66, Zn68, and C13 isotopomers. Data was also obtained for ZnCN in several quanta of its bending mode and in the (100) stretching vibration. These measurements indicate that the most stable form of zinc and the cyanide moiety is the linear cyanide structure, as has also been found for copper and nickel. In contrast, the linear isocyanide geometry is lowest in energy for gallium and aluminum. A spectroscopic analysis has been carried out of the (000) and excited vibrational data, establishing rotational, spin-rotation, and l-type doubling parameters. Several structures (r0, rs, and rm(1)) have been determined for ZnCN as well, along with estimates of the heavy-atom stretch (ω1), and bending (ω2) frequencies. These calculations suggest that the metal–carbon bond in ZnCN is weaker than in CuCN or NiCN. The tendency of these metals to form the linear cyanide geometry, as opposed to the linear isocyanide or T-shaped structures, is additionally discussed.